[dpdk-dev] [PATCH] vfio: support iommu group zero

Alex Williamson alex.williamson at redhat.com
Thu Dec 10 00:22:14 CET 2015


On Wed, 2015-12-09 at 15:12 -0800, Stephen Hemminger wrote:
> On Wed, 09 Dec 2015 23:49:59 +0100
> Thomas Monjalon <thomas.monjalon at 6wind.com> wrote:
> 
> > 2015-12-09 13:58, Stephen Hemminger:
> > > On Wed, 09 Dec 2015 22:12:33 +0100
> > > Thomas Monjalon <thomas.monjalon at 6wind.com> wrote:
> > > 
> > > > 2015-12-09 09:55, Stephen Hemminger:
> > > > > The current implementation of VFIO will not with the new no-IOMMU mode
> > > > > in 4.4 kernel. The original code assumed that IOMMU group zero would
> > > > > never be used. Group numbers are assigned starting at zero, and up
> > > > > until now the group numbers came from the hardware which is likely
> > > > > to use group 0 for system devices that are not used with DPDK.
> > > > > 
> > > > > The fix is to allow 0 as a valid group and rearrange code
> > > > > to split the return value from the group value.
> > > > > 
> > > > > Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> > > > > ---
> > > > > Why was this ignored? It was originally sent on 26 Oct 15 back
> > > > > when IOMMU discussion was lively.
> > > > 
> > > > There was no review of this patch.
> > > > The patch has been marked as deferred recently when it was too late
> > > > to do such feature changes in DPDK code:
> > > > 	http://dpdk.org/dev/patchwork/patch/8035/
> > > 
> > > This is why as a fallback the MAINTAINER has to review the patch
> > > or direct a sub-maintainer to do it. I think almost 2 months is
> > > plenty of time for review.
> > 
> > 27 October was 3 days before the feature deadline.
> > And you have not pinged about it since then.
> > But that's true I have missed the importance of this patch.
> > Would it help to have it integrated today?
> > Are you sure it won't break something else?
> 
> Could the original VFIO submitter from Intel review it.

vfio group 0 has always been valid, but it's unlikely that you'd ever
hit it in regular usage since it will typically be the root bus device.
It's only with no-iommu mode in vfio that it's common, but that's
getting reverted for Linux v4.4, so that may change your priorities
about squeezing this in at the last minute.  Thanks,

Alex



More information about the dev mailing list